Due to recent world events, security has become a very important issue. As a result, video surveillance systems are increasingly being used both commercially and privately to monitor areas for security purposes.
Within the area of video surveillance systems, networked video surveillance technologies are now being used. Unlike conventional closed circuit television (TV) systems, networked video surveillance systems make use of standard network infrastructures, such as Internet Protocol (IP) based network infrastructures, to carry digital video signals and control signals. One advantage of networked video surveillance systems is that they allow video surveillance to be performed over existing networks such as the Internet; IP based local area networks (LANs); or IP-based virtual private networks (VPNs) running on top of a public network such as the Internet.
Typically, a networked video surveillance system comprises one or more storage servers (i.e., generally implemented as a general-purpose computer as known to those in the relevant art), which receive data from one or more video camera servers distributed on a computer network. Such a networked video surveillance system also typically comprises one or more viewing devices (e.g., computers, personal digital assistants (PDA) or phones), which can be used to view live video image data from the camera servers or stored video image data from the storage servers.
Networked video surveillance systems are part of a more general class of networked viewing and recording systems that can be used to view and record image data captured from local or remote networked video cameras. Such networked viewing and recording systems can be used for a wide variety of purposes. For example, such networked viewing and recording systems can be used for security in the surveillance of buildings and vehicles.
Networked viewing and recording systems can also be used for supervision. For example, networked viewing and recording systems can be used for checking the performance of staff within a building, or for checking the performance and progress of staff of contracted companies in remote locations.
Networked viewing and recording systems can also be used for entertainment. For example, such systems can be used for live viewing of sporting events and concerts. Another example use of such a system is for education (e.g., for distance learning).
Conventional networked viewing and recording systems, such as video surveillance systems, typically allow for the display and recording of video image data uploaded to a server from one or more remote video cameras over a network, such as the Internet. Often video image data stored on such a server and associated with a particular camera is not contiguous. This can occur, for example, because recording by the particular camera has been event-triggered or scheduled for specific durations of time only. Thus, no video image data may be stored on the server for that particular camera for a particular period of time, leaving gaps in the video image data for that particular camera.
As a result, when viewing stored video image data in parallel from multiple cameras, served from such a conventional server, the video image data may not remain synchronised. This can lead to an operator mistakenly believing that a network connection has been lost or that gaps in video image data are the result of a high degree of network traffic.